The present invention relates generally to semiconductor fabrication and, more particularly, to a wheel for a conveyor system for transporting semiconductor wafers, a conveyor system for transporting wafers, and a method for transferring wafers from a conveyor system to a wafer processing station.
In the fabrication of semiconductor devices, a variety of wafer preparation operations are performed. FIG. 1 is a schematic diagram of a conventional wafer cleaning system 50. The cleaning system 50 includes a load station 10 where a plurality of wafers in a cassette 14 may be inserted into the system for cleaning. Once the wafers are inserted into the load station 10, a wafer 12 may be taken from the cassette 14 and moved into a brush station 16, which includes a first brush box 16a and a second brush box 16b. The wafer 12 is first moved into first brush box 16a, where the wafer is scrubbed in a solution containing specified chemicals and deionized (DI) water. The wafer 12 is then moved into second brush box 16b, where the wafer is again scrubbed in a solution containing specified chemicals and DI water. After the wafer 12 has been scrubbed in brush boxes 16a and 16b, the wafer is moved into a spin, rinse, and dry (SRD) station 20 where DI water is sprayed onto the top and bottom surfaces of the wafer as the wafer is spun. After the wafer 12 has been dried, the wafer is moved from SRD station 20 to an unload station 22.
To achieve the best throughput productivity in wafer cleaning system 50, wafer 12 must be rapidly and efficiently transported from first brush box 16a to second brush box 16b. In comparison with a conveyor system, a robotic xe2x80x9cpick and placexe2x80x9d system is a slow and inefficient way to transport a wafer from the first brush box to the second brush box. Conventional conveyor systems, however, suffer from the drawback that they are capable of transporting wafers only in a horizontal plane. Consequently, these conveyor systems do not interface efficiently with the equipment, e.g., edge clamp devices, that handles a wafer during processing because either the wafer or the track must be moved to obtain the clearance required to process the wafer.
In view of the foregoing, there is a need for a device that efficiently transports a wafer through a wafer processing station such as, for example, a wafer cleaning system having a first brush box and a second brush box.
Broadly speaking, the present invention fills this need by providing a conveyor system that supports and transports a wafer, yet can be readily moved to separate from the wafer during processing. The present invention also provides a wheel for the conveyor system and a method for transferring a wafer from a conveyor system to a wafer processing station.
In accordance with one aspect of the present invention, a wheel for a conveyor system for transporting semiconductor wafers is provided. The wheel includes a first section for supporting a semiconductor wafer at a first level and a second section for supporting the wafer at a second level, with the first level being higher than the second level. In one embodiment, each of the first and second sections is semicircular. In one embodiment, the first level is substantially the same as a level at which the wafer is subjected to a wafer cleaning operation, and the distance the second level is below the first level is in a range from about one sixteenth of an inch to about three sixteenths of an inch.
In accordance with another aspect of the present invention, a conveyor system for transporting semiconductor wafers is provided. The conveyor system includes a plurality of wheels arranged to transport a semiconductor wafer from a first location to a second location. At least some of the wheels have a first semicircular section for supporting the wafer at a first level and a second semicircular section for supporting the wafer at a second level, with the first level being higher than the second level. In one embodiment, the first location is a first brush box and the second location is a second brush box. In one embodiment, the wheels having the first and second semicircular sections are disposed proximate to a wafer processing station such as, for example, a brush box.
In accordance with yet another aspect of the present invention, a method for transferring a semiconductor wafer from a conveyor system to a wafer processing station is provided. In this method, the wheels of a conveyor system are rotated so that a semiconductor wafer being transported by the conveyor system arrives at a wafer processing station substantially at a level at which the wafer is to be processed in the wafer processing station. Next, the wafer is clamped with edge clamp devices as the wheels of the conveyor system support the wafer. The wheels of the conveyor system are then rotated to move the wheels out of contact with the wafer. The wafer may then be subjected to a wafer processing operation as the wafer is clamped in the edge clamp devices.
In one embodiment, the wafer processing station is a brush box and the wafer processing operation is a cleaning operation. In one embodiment, the edge clamp devices are disposed on wafer rotation rollers. In one embodiment, at least some of the wheels are dual radius wheels having a first section with a first radius and a second section with a second radius, the second radius being configured to provide clearance between the second section and the semiconductor wafer. In this embodiment, the operation of rotating the wheels of the conveyor system so that the semiconductor wafer arrives at the wafer processing station substantially at the level at which the semiconductor wafer is to be processed in the wafer processing station includes controllably rotating at least some of the dual radius wheels so that the first sections thereof support the wafer. In this embodiment, the operation of rotating the wheels of the conveyor system to move the wheels out of contact with the wafer includes controllably rotating the dual radius wheels so that the second sections thereof provide clearance between the dual radius wheels and the wafer.
The conveyor system of the present invention may be integrated into wafer processing stations to provide highly efficient transport of the wafers through the wafer processing stations. In particular, the dual radius wheels of the present invention enable the conveyor system to support the wafer at two distinct levels. Thus, the conveyor system of the present invention is capable of not only transporting the wafers rapidly from station to station, but also of efficiently moving clear of the wafers for processing. Consequently, the conveyor system of the present invention advantageously helps to maximize throughput productivity in a wafer cleaning system.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.